Promoter methylation and immunohistochemical expression of hMLH1 and hMSH2 in sporadic colorectal cancer: a study from India

Abstract

To determine the etiological factors of human colorectal cancer (CRC) we assessed the frequency and prognostic significance of hMLH1 and hMSH2 genes in conjunction with hMLH1 and hMSH2 protein expression in 30 Indian CRC patients. The protein expression and promoter methylation of hMLH1 and hMSH2; Mismatch Repair genes (MMR) were analyzed by immunohistochemistry and methylation-specific PCR (MSP), respectively. A loss of hMLH1 expression was recognized in 4(13.3%) and loss of hMSH2 expression was recognized in 2(6.6%) of 30 CRC cases whereas 50% tumors showed reduced expression of hMLH1 and 33.3% showed reduced expression of hMSH2 protein. One tumor showed a loss of both hMLH1 and hMSH2 expression. Normal nuclear staining pattern of hMLH1 and hMSH2 was observed in almost all the adjoining and normal mucosa. Promoter hypermethylation of the hMLH1 gene was detected in 15 of 30 CRC cases (50%) and of hMSH2 gene was only in 3 of 30 CRC cases (10%). No promoter methylation of hMLH1 and hMSH2 genes was observed in adjoining and normal mucosa. Combination of methylation of hMLH1 and hMSH2 gene was observed in two tumors (6.6%). A significant correlation between histological grade of the tumor, methylation and expression of hMLH1 gene (p < 0.05) was observed. Normal expression of hMLH1 and hMSH2 was seen in all of the unmethylated tumors (100%). Nuclear staining and promoter methylation of hMLH1 and hMSH2 did not significantly influence survival. hMLH1 methylation was common and was significantly correlated with loss of hMLH1 protein expression. In contrast, hMSH2 methylation was infrequent. These findings suggest that the inactivation of MMR gene expression probably via hypermethylation may lead to inactivation of their functions which finally leads to tumor aggressiveness and the immunostaining of hMLH1 protein can be used as a prognostic factor for determining the grade of the tumor.

Pattern of mismatch repair protein loss and its clinicopathological correlation in colorectal cancer in North India

“…25 A recent study from north India by Dubey et al reported MSI-high in 22% patients. 26 Earlier, two studies from India by Pandey et al 27 and Malhotra et al 28 have reported MMR protein loss from 17.8-19.9%. But both had reported their study with only 2 antibodies, i.e.…”

Hypomethylation of mismatch repair genes MLH1 and MSH2 is associated with chemotolerance of breast carcinoma: Clinical significance

“…In HNSCC, 50% of tumors harbored methylation at either or both MLH1 and MSH2 promoters . Methylation of MLH1/MSH2 genes was also associated with colorectal cancers and lung cancers . In pretherapeutic BC, TNBC showed the highest deletion but in NACT‐treated samples, HER2‐enriched type showed the highest deletion hinting toward the differences in the pathogenesis of the molecular subtypes of BC.…”

Hypermethylation of protocadherin γ subfamily A12 and solute carrier family 19 A 1 promoters contributes to the occurrence and metastasis of colorectal cancer

“…Hypermethylation in CpG islands has been demonstrated to be a novel mechanism of tumor suppressor gene silencing ( 7 , 8 ). A number of genes have now been demonstrated to be hypermethylated in colorectal tumors, including APC ( 11 ), MLH1 ( 43 ) and O 6 -methylguanine DNA methyltransferase ( 44 ). For example, the inactivation of the cyclin-dependent kinase inhibitor P16 / CDKN2A / INK4a by methylation leads to the disruption of cell-cycle regulation and potentially provides a growth advantage to affected cells ( 45 ).…”